One of the major objectives set forth for this project was to characterize enzyme profiles in tissues from animals with varying propensities for lipid and protein deposition. We have completed this objective for a number of animal models which represented extremes in body composition (obese-hyperglycemic mouse, Zucker obese rat, Ossabaw vs. Yorkshire pigs and in premigratory induced obesity in avian species). There are two animal models yet to complete, the Ay/a yellow obese mouse and the growth selected mouse. The interpretations placed on these enzyme studies are supported by additional in vitro and in vivo studies using isotopically labeled substrates. The overall shifts in metabolism in the various animal models are being described by these procedures. An example is the lean and obese pig study. In the pig that tends to become fat, the major site for lipid synthesis is the adipose tissue. Uptakes and utilization of glucose, acetate, and glycerol are more rapid in adipose tissue of fat pigs. Amino acids normally utilized for protein synthesis were not more effectively taken up by adipose tissue in the fat pig. The overall utilization of amino acids appears to be decreased in muscle tissue, increased in liver (catabolized) and unaltered in adipose tissue of the fat pig. The next step in determining the factors which regulate the amount and efficiency of protein and lipid deposited is to investigate how these metabolic shifts are produced in animals. Toward this end we are designing experiments to study blood borne growth factors. BIBLIOGRAPHIC REFERENCES: Ezekwe, E.O. and R.J. Martin. 1975. Cellular characteristics of skeletal muscle in selected strains of pigs and mice and the unselected controls. Growth 39: 95-106; Deb, S. and R.J. Martin. 1975. Effects of exercise and of food restriction on the development of spontaneous obesity in rats. J. Nutr. 105: 543-549.